Lubricating compositions

ABSTRACT

LUBRICATING COMPOSITIONS FOR INTERNAL COMBUSTION ENGINES WITH ROTARY PISTONS, WHICH COMPRISE: 90 TO 95% BY WEIGHT OF A LUBRICATING MIXTURE CONTAINING 15 TO 80% OF POLYMER OF AN OLEFIN CONTAINING 4 CARBON ATOMS SELECTED FROM THE GROUP CONSISTING OF HYDROGENATED AND NONHYDROGENATED POLYISOBUTYLENE, POLYBUTYLENE AND THEIR MIXTURES, HAVING A MEAN MOLECULAR WEIGHT OF BETWEEN 250 AND 2000, AND 85 TO 20% OF LUBRICATING OIL, 0.5 TO 2.5% OF ANTI-WEAR ADDITIVE, WITH THE REMAINDER OF THE COMPOSITIONS BEING USUAL ADDITIVES FOR 2-STROKE AND 4-STROKE ENGINES.

United States Patent US. Cl. 252--32.7 E 8 Claims ABSTRACT OF THE DISCLOSURE Lubricating compositions for internal combustion engines with rotary pistons, which comprise: 90 to 95% by weight of a lubricating mixture containing 15 to 80% of polymer of an olefin containing 4 carbon atoms selected from the group consisting of hydrogenated and nonhydrogenated polyisobutylene, polybutylene and their mixtures, having a mean molecular weight of between 250 and 2000, and 85 to 20% of lubricating oil, 0.5 to 2.5% of anti-wear additive, with the remainder of the compositions being usual additives for 2-stroke and 4-stroke engines.

This invention is a continuation-in-part of application Ser. No. 73,572, filed Sept. 18, 1970; in turn a continuation-in-part of our copending application Ser. No. 555,050, filed June 3, 1966, and now abandoned; in turn a continuation-in-part of our copending application Ser. No. 73,575, filed Sept. 18, 1970, now Pat. No. 3,753,905, issued Aug. 21, 1973; in turn a continuation-in-part of application Ser. No. 778,858, filed Nov. 25, 1968, and now abandoned, and relates to lubricating compositions which are particularly suitable for internal combustion engines with rotary pistons, which will be hereinafter referred to as rotary engines.

Much work has been devoted within recent years to the development of rotary engines of the Wankel type. These engines have a three-sided rotor mounted on an eccentric which is carried on a central shaft. Such engine offers the advantage of generating rotation directly, while the classical reciprocating engines must convert linear motions to rotary motion.

Some effort has been directed to the lubrication of IO- tary engines which require specific lubricating qualities due to their conception. In a rotary engine, the lubricating composition has two purposes. First, a small amount of lubricant is injected into the fuel for lubricating the stator flanks and rings and for securing the tightness of the seals, such as apexes and side seals. Second, major amount of lubricant must be circulating under pressure on the rotor brushings and the crankshaft bearings.

The lubricating oil generally is added in admixture with the fuel. Such lubricating oil must therefore be eliminated from the combustion chamber and must leave practically no deposit therein in order to avoid any preignition and ring sticking. Moreover, the temperature of rotary engines in normal operation is higher than with conventional 4- stroke engines. Thus, the lubricating film must fulfill specific properties as regards viscostability and thermal stability. Also, a rotary engine is only upheld by two bearings while conventional 4-stroke engines include at least four bearings. As a result, the oil film is subjected to higher pressures in a rotary engine. Therefore, lubricating composition for rotary engines must not only exhibit the qualities of both lubricants for 2-stroke engines and lubricants for 4-stroke engines, but also must meet spe- 3,838,049 Patented Sept. 24, 1974 cific and severe requirements of mechanical and thermal resistance.

Lubricating compositions containing polyisobutylene as a primary component have been disclosed. In such compositions, polyisobutylene is in admixture with a lubricating oil in an amount which is at least equal to the amount of said oil. Such compositions have given satisfactory results, but additional reserach work has been deemed desirable to raise further the qualities of such compositions and to improve their performance particularly under severe conditions and for extended periods of time.

It is an object of the present invention to provide new and novel lubricating compositions.

Another object of the present invention is to provide new improved lubricating compositions containing polyisobutylene polymers.

An additional object of the present invention is to provide a new and improved lubricating composition particularly useful in rotary engines.

Additional objects will become apparent from the following descriptions of the invention herein disclosed.

SUMMARY OF THE INVENTION These new and improved lubricating compositions for internal combustion rotary engines comprise (1) 90 to 95% by weight of a lubricating mixture containing 15 to of polymer of an olefin containing 4 carbon atoms and selected from the group consisting of hydrogenated and non-hydrogenated polyisobutylene, polybutylene and mixtures thereof, having a mean molecular weight of between 250 and 2000, and to 20% of lubricating oil, (2) 0.5 to 2.5% of anti-wear additive, and (3) the remainder of the composition being conventional additives for 2-stroke and 4-stroke engines.

PREFERRED EMBODIMENTS The lubricating mixture which is the major part of the compositions of the present invention contains from 15 to 80% of polybutene and/or polyisobutylene, hydrogenated or nonhydrogenated, having a mean molecular weight of between 250 and 2000, such polymers being hereinafter referred to as Poly-C These polymers are manufactured from fractions containing hydrocarbons with 4 carbon atoms, the main constituents being mono-olefins generally in admixture with saturated hydrocarbons. Such fractions, which generally are free of diolefinic and acetylenic hydrocarbons, are polymerized, most often in the presence of a Friedel-Crafts catalyst. In many instances, the polymers obtained contain polybutylene and polyisobutylene in varying proportions. Generally, such mixed polymers may contain about 5 to 70% of polyisobutylene and to 30% of polybutenes. These polymers generally have an unsaturated terminal group, which, however, may be saturated by hydrogenation.

Comparative tests have been carried out with the lubricating compositions of the present invention containing, as the polymer, primarily polybutene and primarily polyisobutylene. The results have shown that lubricating compositions prepared using either of such polymers are sim- Some viscostability tests of Poly-C having molecular weight lower than 2000 have shown that non-hydrogenated Poly-C is more stable than the hydrogenated Poly-C By contrast, other tests do not point out a difference between these different types of polymers. These somewhat inconsistent results are proving that laboratory tests are not always suitable to estimate lubricants having to work under severe mechanical and thermal conditions and that road trials are the only conclusive tests. Such road trials have shown that hydrogenated and non-hydrogenated Poly-C have practically equivalent performance as regard as viscostability.

The amount of Poly-C in the lubricating composition may be varied between relatively large ranges from 15% to 80% by weight of the lubricating mixture which forms the major part of the composition. Wear tests carried out with compositions containing varying amounts of Poly-C have shown that compositions with at least 15 of Poly-C have better anti-wear characteristics than similar but Poly-C -free compositions. This improvement increases when the amount of polymer is increased and is particularly important when this amount is lying between 25 and 75% by weight. Moreover, a noticeable reduction of opacity and of burned oil odor of the exhaust gases results from the use of lubricating compositions containing Poly-C in such amounts. Generally, Poly-C with a lower molecular weight may be used in amounts up to 80% by weight and Poly-Cis with higher molecular weights ranging from about 1000 to 2000, are preferably employed in lower amounts, more particularly between 15 and about 40% by weight.

Motor tests carried out with lubricating compositions containing 90 to 95% of Poly-C and 10 to 5% of usual additives have shown that these oils in admixture with a fuel are burned without deposit of solid products. However, some parts of the motor were found to be dry and were worn abnormally. This disadvantage may be obviated by adding lubricating oil to the compositions, said oil providing a stable and unctuous lubricant film on the moving parts of the motor. The required amount of oil is at least 20% based on the weight of lubricating mixture in said compositions.

The lubricating oil may be a mineral oil or a synthetic, organic oil, such as an adipic, azealic, sebacic acid ester of an aliphatic alcohol containing from 8 to 20 carbon atoms, for example Z-ethylhexanol, decanol, dodecanol, octadecanol. A mixture of mineral and synthetic oils in varying amounts also may be used. The preferred mineral oils are solvent refined oils and it has been observed that with the additives as stated above, paraffinic oils as well as naphthenic oils are suitable. Oils or blends of oils having a viscosity generally between about 80 and 110 SSU at 210 F. or 8 to 18 centistokes at 210 F. preferably are used.

Compositions containing a lubricating oil and Poly-C offer advantages which are significant in comparison with conventional lubricants when used in rotary engines. Since some parts of the motor and more particularly bearings and bushings, are subjected to high pressures, lubricating compositions for these engines must exhibit anti-wear characteristics which generally are not required of lubricants for 2-stroke and 4-stroke engines. Accordingly, it is necessary to incorporate into the mixture of lubricating oil and Poly-C an anti-wear additive, more particularly a metallic salt of dialkylphosphoric or dialkylthiophosphoric acid, preferably a zinc salt of these acids. It has been found that the improvement with respect to anti-wear properties is noticeable when the amount of this additive is as low as 0.5% by weight of the composition. This unexpected result may be due to the fact that the Poly-C is improving the wear characteristics of the lubricant and that the additive response of some products in Poly-C is improved. On the basis of results obtained from road trials, it has been found that the amount of anti-wear additive may be kept lower than 2.5% based on the weight of the composition and that, due to the synergistic effect between the additive and Poly-C this amount preferably is between 0.5 and 1.5% by Weight.

As a result of the specific design of the rotary engines and the mechanical and thermal conditions the lubricant must withstand, it is necessary to employ a composition containing a lubricating oil, Poly-C and anti-wear additive in the proportions as stated above. Moreover, the Poly-C must have a mean molecular weight comprised between 250 and 2000. By modifying the proportions of the components or by using a Poly-C having a molecular weight outside the above range, the performance of the lubricating compositions for rotary engines is substantially altered. For example, the use of polyisobutylene having a molecular weight higher than 2000, namely a Poly-C with a molecular weight of 5000, gives rise to the formation of varnishes in the combustion chamber. Moreover, compositions containing high molecular weight Poly-C s or other high molecular weight polymers produce ring sticking, resulting in an increase in wear. Therefore, it is highly important to select the components of the lubricating composition and their respective amounts in accordance with the herein provided instructions in order to improve the performance of the rotary engines.

The operation temperature of rotary engines is somewhat higher than with usual reciprocating engines and it is convenient to avoid any trouble with respect to heat exchange. When the novel lubricant is used with leaded motor fuel, it may be advantageous to add a lead-scavenging agent to avoid the formation of deposits on the rings. Such deposits give rise not only to the scratching of these rings, but also to a decrease in the heat-exchange etficacy. The lead-scavenging agent most often employed is a halogenated aliphatic or alkylaromatic hydrocarbon and generally is used in an amount varying from 0.5 to 1.5 by weight of the lubricating composition.

Other usual additives such as detergent or dispersing agents, ashless additives, viscosity index improvers, oxidation inhibitors, etc., and mixtures thereof also may be added to the compositions of this invention. When em ployed, the total amount of such additives usually is between about 1 and 10% of the composition. The detergent agents generally are oil soluble petroleum sulfonates, more particularly calcium or barium petroleum sulfonates. Viscosity index improvers, preferably oil-soluble polymers of esters of unsaturated carboxylic acids, for example polymers of esters of acrylic or methacrylic acid and C to C alcohols, are used in varying amounts, which may be as high as 6 to 7% by weight of the composition in the case of multi-grade type compositions. The compositions according to this invention have a viscosity of between 17 and 23 centistokes at 210 F.

The following examples further illustrate the invention which is not to be construed as limited thereby.

\ EXAMPLE 1 Lubricating compositions have been prepared from the following components:

Mineral oil (solvent refined coastal) (75 SSU at F.).

Poly-C with a mean molecular weight of about 300 (Poly-C 300).

Poly-C with a mean molecular weight of about 650 (Poly-C 650).

Hydrogenated Poly-C with a mean molecular weight of about 500 (Poly-C H 500).

Zinc dibutylthiophosphate.

Lead scavenging agent. 1

Calcium petroleum sulfonate.

Viscosity index improver (polyacrylate type).

These components have been used in varying amounts as given in Table I below.

The lubricating compositions prepared from these components have been tested on R 100 engines (of Toyo Kogyo Cy) for 100 hours and the results also are given TABLE'I Compositions according to the invention Comparative 1 2 3 4 5 lubricant Mineral oiL Thiophosphate Lead seavengen. Ca petroleum su VI improver Weight loss (in mg.

Apex seals Corner seals Side seals Total loss In order to illustrate that the components of the compositions of the," present invention must satisfy the above stated specifications with regard to the respective amounts and the selection of these components, comparative tests have been carried out.

Comparative test A.Composition 1 of Table I was duplicated except that a Poly-C having a molecular weight of about 6000 was used instead of Poly-C 300. The total weight loss of the seals was 1257.8 mg. and varnishes were formed on the rings.

Comparative test B.Composition 1 of Table I was again repeated'except no lead scavenger was used. The total weight loss was 1057.8 mg.

Comparative test C.Composition 1 of Table I was again repeated except that the thiophosphate was not used. A high loss of oil was observed after a 15,000 km. test, this loss resulting from a marked wear on the bearings.

Comparative test D.A composition was prepared without mineral oil, but with 92.5% of Poly-C 300 and the additives of Composition 1. A test for 100 hours illustrated that:

the wear of the seals was marked: 1402.3 mg. the seals were dry and burned.

Comparative test E.A composition was prepared from 92.5% mineral oil and 7.5% of the additives mixture of Composition'l and without Poly-C After 100 hours, the wear of the seals was particularly high: 1953.2 mg.

The comparison of the results obtained with Compositions 1 to 5 and comparative tests C and E show the synergistic effect resulting from the use of Poly-C together with an anti-wear agent. The comparative test B illustrates the improvement resulting from the use of lead scavenging agent when leaded fuels are employed with the rotary engines. Comparative test D indicates the beneficial effect of using a mineral oil in conjunction with Poly-C the mixture being more unctuous and forming uniform and stable oil films.

EXAMPLE 2 A lubricating composition was prepared from:

46% of Poly-C with a mean molecular weight of 600 46% of mineral oil (solvent refined coastal) 2% of zinc dibutylthiophosphate 1.5% of lead scavenging agent 3% of Ca petroleum sulfonate 1.5% of V1. improver.

Road trials have been carried out for 75,000 km. with a rotary engine NSU KKM 502 (50 I-I.P.; 6,000 r.p.m.). It was observed during these trials that the octane requirement was not increased, the fuel employed having an octane index of between and 85, without power loss. Such tests illustrated that the lubricating compositions of the present invention result in a minimum of deposits in the combustion chamber and in the exhaust port. With lubricating compositions containing no Poly-C the power loss of the engine was noticeable after about 40,000 km.

EXAMPLE 3 A lubricating composition was prepared from:

50% of Poly-C having a mean molecular weight of 600 25% of mineral oil 21% of dioctylphthalate 7% of the same additives as in Example 2.

Tests were carried out on rotary engine R 100. Such tests resulted in a total weight loss of the seals of only 787.4 mg. Moreover, the engine was exceptionally clean and without sticking or varnishes.

EXAMPLE 4 The composition of Example 2 was duplicated using polyisobutylene with a mean molecular weight of 900 instead of Poly-C 600.

A Mazda car with rotary engine R 100 has been running for 100,000 km. with this lubricant, without any problem. No lack of compression due to ring sticking has been observed. Moreover, the internal engine surfaces were perfectly smooth.

What is claimed is:

1. Lubricating composition for internal combustion engines with rotary pistons comprising:

90 to 95% by weight of a lubricating mixture containing 15 to 80% of polymer of an olefin containing 4 carbon atoms selected from the group consisting of hydrogenated and unhydrogenated polybutylenes and mixtures thereof, having a mean molecular weight between 250 and 2000, and to 20% of a lubricating oil, selected from the group consisting of mineral lubricating oil and organic esters of a dibasic acid having from 6 to 8 carbon atoms with an aliphatic alcohol having 8 to 20 carbon atoms, said lubricating oil having a viscosity in the range of about 80 to 110 SSU at 210 F.;

0.5 to 2.5% of anti-wear additive, and

from to 10% of a detergent 0r dispersant additive, a viscosity index improver, an oxidation inhibitor, a lead scavenging additive and mixtures thereof.

2. The lubricating compositions of Claim 1 wherein said polymer has a molecular weight of between 250 and 1000.

3. The lubricating compositions of Claim 1 wherein said lubricating oil has a viscosity of between 8 and 18 centistokes at 210 F.

4. The lubricating compositions of Claim 1 wherein the amount of said anti-wear additive is between 0.5 and 1.5% by weight. 7

5. The lubricating compositions of Claim 1 having a viscosity of between 17 and 23 centistokes at 210 F.

6. Lubricating composition according to claim 1 wherein the said anti-wear additive is a member of the group consisting of zinc dilower alkyl phosphate and zinc dilower alkyl thiophosphate.

7. Lubricating composition as defined in Claim 1 wherein the lubricating oil ester is a member of the group consisting of esters of adipic, phthalic, azealic and sebacic acids esterified with an alcohol of the group consisting of 2- ethyl hexanol, octanol, decanol, dodccanol and octadecanol.

8. Method of lubricating a rotary piston engine comprising lubricating the moving parts of said engine with a lubricating composition comprising:

to by weight of a lubricating mixture contain ing 15 to 80% of polymer of an olefin containing 4 carbon atoms selected from the group consisting of hydrogenated and unhydrogenated polybutylenes and mixtures thereof, having a mean molecular weight between 250 and 2000, and 85 to 20% of a lubricating oil, selected from the group consisting of mineral lubricating oil and organic esters of a dibasic acid having from 6 to 8 carbon atoms with an aliphatic alcohol having 8 to 20 carbon atoms, said lubricating oil having a viscosity in the range of about 80 to 110 SSU at 210 F;

0.5 to 2.5% of anti-Wear additive, and

from 1 to 10% of a detergent or dispersant additive, a viscosity index improver, an oxidation inhibitor, a lead scavenging additive and mixtures thereof.

References Cited UNITED STATES PATENTS Voltz 25259 X Benoit 25251.5 A Benoit 2525l.5 A Guminski 25259 X Brown 25259 X Olund 25259 Olund 25259 Dyer 25259 X OTHER REFERENCES Norbye: The Wankel Engine (1971), pp. 40 and 329.

WARREN H. CANNON, Primary Examiner US. Cl. X.R.

1 ,838,049 Dated September 24 1974 Patent No.

Inventor) Georges Jules Souil lar d et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 6, line 45; after "froifi" insert 1 Signed and sealed this 28th day of Januar 1975.

sEALf Attestz" MCCOY IYI. GIBSON JR. C. MARSHALL DANN Attest ng Officer Commissioner of Patents u'scoMM-Dc scene-P69 U.S. GOVERNMENT PR NTING OFFICE: 869. 930

FORM PO-1050 (10-69) 

